Electron sensitive color photographic plate



June 1948. E. G. RAMBERG 2,442,961

ELECTRON SENSITIVE COLOR PHOTOGRAPHIC PLATE Filed Jan. 23, 1946 ATTORNEY Patented June 8, 1948 ELECTRON SENSITIVE COLOR PHOTO- GRAPHIC PLATE Edward G. Bamberg, Feasterville, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application January 23, 1946, Serial No. 642,949

(Ci. 25o-65) 12 Claims. 1

This invention relates generally to electron photography and more particularly to electron color photographic plates responsive to variations in the velocity of electrons impinging thereon.

Frequently it is desirable to record differences in the velocity of electrons impinging upon the photographic plate employed in electron optical systems such, for example. as an electron microscope. When constant velocity electrons are applied to irradiate a microspecimen in an electron microscope, variation in the velocity of electrons derived from the specimen may be interpreted in terms vof the materials comprising the specimen or of variations in the thickness of the specimen. The instant invention contemplates the use of a color photographic plate capable of recording diierences in the velocity of electrons impinging thereon in terms of the color or'colors oi the developed and fixed plate when viewed by light transmission.

The color plates according to the invention essentially are similar to the Paget color process plates comprising a plurality of mosaics having diierent photographic color properties such, for example, as complementary ne checkerboard patterns of alternate red and green dye patches covering a supporting plate. The essential difference between conventional color process plates and the photographic color plate of the instant invention is that a thin, uniform-thickness, metallic iilm is deposited over all of the rectangular dye patches of one of the color mosaics. and then the second color mosaic is deposited over the thinpmetallic iilm. l

In the U. S. Patent 2,372,170 granted to Rich ard F. Baker on March 27, 1945, it is shown that various photographic materials have maximum sensitivity to irradiating electrons of a predetermined electron velocity. Electron velocities greater or less than the optimum value provide reduced exposure of the photographic film. This principle is utilized in the instant invention by selecting electron velocities in the minimum range which will provide emcient exposure of the outer color iilm, and thence selecting the character and thickness oi the metallic iilm between the color nlms to provide the desired optimum electron velocity difference for exposure of the second color photographic iilm under the metallic nlm. Thus if both photographic lms have maximum electron sensitivity at 50 kilovolt electron velocity. and the thickness of the metallic deposit is suflicient to reduce the velocity of 70 kilovolt electrons to an eilective value of 50 kilovolts, then the outer color nlm will provide maximum 'sensitivity for 50 kilovolt electrons while the inner color lm will have maximum sensitivity to kilovolt electrons.

Portions of the photographic plate exposed to 50 kilovolt electrons will be blackened most at the squares of the mosaic comprising the outer color nlm. Similarly portions of the plate exposed to 70 kilovolt electrons will be blackened most at the complementary squares of the mosaic comprising the inner photographic lilm. When viewed by lightl transmission, the photog.aphic\ plate thus will provide distinguishing color characteristics depending upon the velocities of the electrons which impinged upon the plate.

Among the objects of the invention are to provide an improved method of and means for measuring electron velocities. Another object is to provide an improved method of and means for recording diierences in electron velocity. An additional object is to provide an improved method of and means for producing a color record of differences in the velocity of electrons impinging upon a color plate. A further object is to provide an improved color plate for electronoptical photography for indicating diierences in the velocity of electrons exposing said plate. A still further object of the invention is to provide an improved color plate for electron optical photography comprising complementary mosaics of electron sensitivematerials having diierent elec-4 tron-velocity sensitive characteristics, or providing distinguishing color characteristics for different impinging electron velocities. Another object is to provide an improved method of and means for indicating photographically the composition of microspecimens in an electron microscope -or other electron optical device.

The invention will be described in further detail by reference to the accompanying drawing of which Figure 1 is a plan view of a color plate in accordance with the invention, Figure 2 is a side elevational schematic view of the basic combination of such a color plate with an irradiating electron source, and Figure 3 is a family of graphs illustrating 4the electron velocity-sensitive characteristics of a typical pair of electron sensitive films according to the invention. Simi-- lar reference characters are applied to similar elements throughout the drawing.

Referring to Figuresl and 2 of the drawing, the electron-sensitive color plate according to the invention includes'for example, a glass support I upon which is deposited a large number of rectangular red dye patches forming a red screen 3 and arranged in a checkerboard pattern as shown in Figure 1. Over the layer of red dye patches 3' is deposited a thin metallic lm 5, such as magnesium, which reduces the velocity of '70 kilovolt electrons to an eilective velocity of 50 kilovolts. Over the metallic lm 5, a second electron-sensitive color screen 1 is deposited in a similar line checkerboard pattern of alternate green dye patches l wherein the green patches coincide with the spaces between the red dye patches 3 of the red screen 3.

It should be understood that any other combination of electron-sensitive color screens may be employed and that the arrangement and orientation thereof may be varied in any desired manner. For example, instead of rectangular checkerboard patterns, the screens may comprise circular, hexagonal, or other shaped dye patches alternately or randomly arranged, or they may comprise alternately spaced color lines of any desired color arrangement. Furthermore more than two such screens may be superposed, and the metallic film 5 may or may not be interposed between each of the screens. Also the screens and the metallic lm may be applied in any known manner such as by evaporation, electrodeposition or by conventional coating processes, including or excluding the use of masking screens.

In a typical example, red and green checkerboard electron-sensitive color screens separated by a thin magnesium deposit are employed as shown in the drawing. The color screens 3 and 1 have maximum electron photosensitivity for electron velocities of 50 klovolts. The thickness of the metallic deposit 5 is selected to require an electron velocity of 20 kilovolts for penetration thereof. Preferably, the electron decelerating deposit 5 should be substantially transparent; to light transmission. However. if desired, lt may be dissolved away during development of the color screens.

The portions of the color plate bombarded by 50 kilovolt electrons derived from an electron source 9 will be blackened most (after development and fixing), at the green squares 'I' on the green color screen 1. Similarly, electrons having a velocity of 70 kilovolts will provide maximum blackening of the red color patches 3' of the red screen 3, since such'70 kilovolt electrons will be decelerated by 20 kilovolts` in passing through the metallic deposit 5 between the color screens, The blackening of the red dye patches by 50 kilovolt electrons therefore will provide an apparent increase in the green transmission of the color plate when viewed by light transmission. Similarly the blackening of the green dye patches by 70 kilovolt electrons Will apparently increase the red light transmission of the color plate.

For a certain electron velocity between 50 and '70 kilovolts, the color screen passes from a greenish to a reddish coloration when viewed by light transmission. For electron velocities below 50 kilovolts, the color screen will have more pronounced red transmission, while for electron velocities above 70 kilovolts the screen will appear to have somewhat less pronounced green light transmission characteristics. As explained heretofore other dye patch arrangements or combinations will provide different color properties in response to different bombarding electron velocities.

In Figure 3 the electron photosensitivity of the green and red screens 'I and 3, respectively, is illustrated in the graphs I1 and I3.

The color screen thus described may be employed for velocity analysis of an electron image as in an electron microscope, (not shown), wherein substantially constant velocity electrons irradiate a microspecimen, and the variations in velocity of electrons transmitted by the specimen may be employed to determine the molecular composition or the thickness of the various portions of the imaged specimen. Color plates of the type described also may be employed for any other purpose wherein measurements of electron velocity are desired over predetermined velocity ranges. The exposed color screen may be observed by light transmission in any desired manner.

It should .be understood that if the outer color screen 1 provides appreciable electron deceleration through the portions of the screen between the dye patches, the metallic deposit 5 may be omitted since the additional deceleration provided thereby may not be required. Various combinations of color screens and decelerating films or deposits may be employed to provide additional color differentiation for indicating more extended electron velocity ranges.

I claim as my invention:

1. A photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive materials having dierent electron-velocity photosensitivity characteristics and disposed in parallel complementary relation, whereby contrasting exposure of said mosaics is provided by irradiating electrons of predetermined different velocities.

2. A photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive ymaterials having diierent electron-photosensitivity characteristics and disposed in parallel complementary relation, and an electron decelerating element disposed between said mosaics whereby contrasting exposure of said mosaics is provided by irradiating electrons of predetermined different velocities.

3. A photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive materials having different electron-photosensitivity color characteristics and disposed in complementary interleaved relation, and an electron decelerating element disposed between said mosaics whereby contrasting exposure of said mosaics is provided by irradiating electrons of predetermined diiferent velocities.

4. In a system utilizing a photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive materials having different electronphotosensitivity characteristics and disposed in parallel complementary relation, and an electron decelerating element disposed between said mosaics whereby contrasting exposure oi said mosaics is provided by irradiating electrons of predetermined diilerent velocities, the method comprising irradiating said mosaics simultaneously by electrons of predetermined different velocities to provide contrasting exposures of said mosaics as a function of said irradiating electron velocities, and developing said exposed mosaics to pro-- vide color contrast therein.

5. The method according to claim 4 including the step of removing said decelerating element subsequent to electron exposure oi' said mosaics.l

removing at least portions of said deposited element subsequent4 to electron exposure of said mosaics.

7. In combination, a photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive materials having dierent electron-photosensitivity colo'r characteristics and disposed in parallel complementary relation, and an electron decelrating element disposed between said mosaics, and means for' irradiating said mosaics simultaneously by electrons of predetermined dierent velocities to provide contrasting color exposure of said mosaics.

8. Inl combination, a photosensitive plate for electron-optical photography comprising a pair of mosaics oi electron photosensitive materials having diierent `electron-photosensitivity color 4 characteristics. and disposed in parallel complementary registry, and an electron decelerating element disposed. between said mosaics, and

means for irradiating said mosaics simultaneously by electrons of predetermined ditl'erent velocities to provide contrasting color exposure of said mosaics.

9. In combination, a photosensitive plate for electron-optical photography comprising a pair of checkerboard mosaics of electron photosensitive materials having different electron-photosensitivity color characteristics and disposed in parallel complementary registry, and an electron decelerating element disposed between said mosaics, and means for irradiating said mosaics simultaneously by electrons of predetermined diierent velocities to provide contrasting color exposure of said mosaics.

10. A photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive materials having different electron-photosensitivity characteristics and disposed in parallel complementary relation, and a substantially optically transparent electror decelerating element disposed between said mosaics whereby contrasting exposure of said mosaics is provided by irradiating electrons of predetermined different velocities.

11. A photosensitive plate for electron-optical photography comprising a pair of complementary mosaics of electron photosensitive materials having different electron-photosensitivity characteristics and disposed in paralle1 complementary relation, and a thin metallic electron decelerating element disposed between said mosaics whereby contrasting exposure of said mosaics is provided by irradiating electrons of predetermined diierent velocities.

12. A photosensitive plate for electron-optical photography comprising a pair of complementary mosaics o1'electron photosensitive materials having different electron-photosensitivity characteristics and disposed in parallel complementary relation, and a thin magnesium illm comprising an electron decelerating element disposed between said mosaics whereby contrasting exposure of said mosaics is provided by irradiating electrons of predetermined diierent velocities.

EDWARD G. BAMBERG. 

